In recent years, unprecedented prosperity has appeared in the R&D and innovations of the technology of broadband wireless access. The IEEE 802 serial standards are developed rapidly, and technologies such as IEEE 802.11 and 802.16 become the focus in the wireless communication industry. In the broadband wireless access networks, as to the downlink, the base station transmits broadcast control data and data traffic in the way of point-to-multipoint. As to uplink, multiple mobile stations share the transmission medium through TDMA/OFDMA/FDMA/CDMA techniques to transmit data traffic or control information, e.g. bandwidth allocation request messages to the base station.
One commonly used way of resource allocation is contention-based bandwidth request. As shown in FIG. 1, firstly, in step S11, the BS broadcasts to MSs the UL-MAP in which the BS assigns resource block of bandwidth request region (BR Request Region) for receiving random BR-Req CDMA signals sent by the MSs for requesting bandwidth, so as to carry out bandwidth requesting. Then, in step S12, the MS sends a random BR-Req CDMA signal for requesting bandwidth to BS in the BR Request Region and starts a timer. Next, in step S13, the BS detects data received in the BR Request Region, determines the CDMA code used by MS in the data, and allocates dedicated time/frequency resource for each correctly-detected CDMA code. The information of the dedicated time/frequency resource is placed in the CDMA_Alloc_IE information in the UL-MAP and sent to each MS. The CDMA_Alloc_IE information contains the CDMA code identification detected by the BS, the size and location, of the allocated dedicated resource and the used modulating and encoding schemes. After that, in step S14, each MS keeps monitoring the UL-MAP sent by the BS, and if one MS obtains the CDMA_Alloc_IE information before the timer overflows, it sends a bandwidth allocation request message, namely a BR-Req header, in the corresponding time/frequency resource indicated by the CDMA_Alloc_IE information. The bandwidth allocation request message contains the size of the bandwidth requested by the MS and the connection ID (CID) of the traffic flow that requests this bandwidth. If one MS doesn't receive the CDMA_Alloc_IE information containing the CDMA code that the MS previously sent, the MS increases the transmitting power of the CDMA bandwidth request and starts a new procedure of bandwidth request from step S11.
The drawback of the procedure of the contention-based bandwidth request lies in that: the interactions between the BS and the MS are much frequent. If the MS doesn't receive a CDMA_Alloc_IE information, sent by the MS, in step S14, the MS selects a new CDMA code to re-transmit after a certain period of time. For real-time interactive traffic, this kind of latency maybe is hard to bear. Therefore, it is necessary to improve the way of bandwidth request and allocation.